The present invention relates to an oil leakage preventive method. More particularly, the present invention relates to an oil leaking preventive method wherein a repair work for a potential transformer from which oil leaks is simply and quickly carried out.
When electric current of a high voltage transmitted from a power station is transformed to that of an ordinary voltage to be used, a potential transformer has been used.
The potential transformer T, as shown in FIG. 8, comprises a metal body 20 in a form of a specific box, a packing 21, a canopy 22 provided on the body through the packing 21, a packing 23, a conservator 24 disposed on the canopy 22 through the packing 23, bushings 25 and necessary equipments such as a radiator, not shown.
A core 26 and coils 27 are received in the body 20, and potential transformer oil 28 such as mineral oil is also contained therein to insulate and cool the core 26 and coils 27. The oil 28 is tightly sealed in the body not to leak through the packing 21.
The packing used for the potential transformer is formed of nitrile rubber as a main raw material, and a vulcanized substance of nitrile rubber or a vulcanized substance of a mixture of nitrile rubber and cork is usually used.
However, although the packing comprising the nitrile rubber as a main material is generally satisfactory for an oil-resistant property and an earthquake-resistant property, the packing deteriorates in a short period of time due to a low heat-resistant property of the packing against heat such as Joule's heat generated during operation of the potential transformer, so that oil leakage is incurred.
In such a case, of course, the deteriorated packing can be replaced with a new packing. However, for instance, a large potential transformer having approximately a rated capacity of 3,600 KVA and a rated power of 33,000 V weighs several tens of tons, so that it is very difficult to lift a canopy of the potential transformer for exchanging the deteriorated packing with a new one, which requires a long period of time and a high cost for exchanging bolts and with a wrecker.
Moreover, in case a potential transformer is installed in a building, when a canopy is removed, a beam of a wrecker may be interrupted by a ceiling of the building, so that the canopy cannot be lifted. Therefore, in this industry, a portion where oil leakage occurs has been repaired by coating a sealing agent 29.
The sealing agent comprises liquid A prepared by mixing 40 to 70 parts of a liquid epoxy resin and 30 to 50 parts of an inorganic filler and having a viscosity of 300,000 to 1,000,000, and liquid B prepared by mixing 40 to 60 parts of liquid polysulfide rubber and 30 to 50 parts of an inorganic filler and having a viscosity of 300,000 to 1,000,000. (Japanese Patent Publication No. Hei 3-2917)
However, there has been a problem such that since the sealing agent requires a long period of hardening time, if the potential transformer is operated before the sealing agent is completely hardened, the intimate contact of the sealing agent is weakened by an oil pressure therein and complete sealing effect cannot be obtained. Further, the long period of hardening time delays resumption of the operation of the potential transformer, which results in a secondary detrimental effect due to electric power suspension as well as unsuitability for a work which requires quick hardening.